@keyframes fade-in {
    form {
        visibility: hidden;
        opacity: 0;
    }
    to {
        visibility: visible;
        opacity: 1;
    }
}

@keyframes fade-out {
    form {
        opacity: 1;
    }
    to {
        opacity: 0;
    }
}

/* vue过渡 */
.fade-enter,
.fade-leave-to {
    opacity: 0;
}
.fade-enter-active,
.fade-leave-active {
    transition: opacity .5s;
}